TECHNICAL FIELD
[0001] The invention generally relates to an apparatus for continuous casting of metal ingots
and apparatus for starting or restarting such machines after they have been stopped
for use therewith.
BACKGROUND ART
[0002] Horizontal continuous casting is commonly used in the production of metal ingots
from molten metal. Continuous casters can produce ingots of various cross-sectional
shape and girth, by varying the casting mould used in the caster. Ingots can then
be cut to desired lengths downstream of the caster. An example of a conventional horizontal
continuous caster can be seen in, for example,
US Patent No. 3,455, 369.
[0003] Multi-strand horizontal casters are a particular type of caster, which allow multiple
strands of ingots to be cast at the same time. Such casters generally have a molten
metal feed trough connected to multiple casting moulds either via a single header
box or via dedicated separate connecting troughs for each mould.
[0004] It is often required to temporarily isolate and shut down one or more strands in
a multi-strand caster. Possible reasons for shutdown include upsets in either upstream
or downstream operations, undesirable conditions of the molten metal, or general maintenance
and repair of the caster. Improper isolation of the particular connecting trough during
shut down can lead to loss of costly molten metal. There is also the possibility of
fires or explosions if molten metal is not collected properly or comes into contact
with water that is often used in cooling the ingots.
[0005] Attempts have been made to isolate and drain particular strands and collect molten
metal during shutdown. An example of such a shut-off device can be seen in
US Patent No. 4,928, 779. However, such devices often require that the molten metal travel through the connecting
trough and the casting mould and drain through the casting mould exit. This can cause
molten metal to solidify in the casting mould and reduces access to this part, in
case of repairs. As well, many shutdown systems only isolate the trough after molten
metal has been sensed at the casting mould exit, so large quantities of molten metal
are lost before the trough is isolated.
[0006] After the caster has been shut-down, and indeed at a time that the caster is to be
started or restarted, it must operate in a manner that is both safe and minimizes
any start-up losses of molten or cast metal. A common concern in start-up is proper
alignment of the cast ingot as it travels towards the cutting equipment. As well,
metal leaving the casting mould is generally direct chilled by coolant sprays that
impinge on the emerging ingot. In start up, it is important to prevent contact between
the coolant and the molten metal, which can lead to explosions and fires.
[0007] Several start-up blocks have been devised for use with horizontal continuous casters.
Some examples of these are shown in
US Patent numbers 4,454,907,
4,252,179,
3,850,225 and
4,381,030. However, most of these devices do not positively seal against the mould to prevent
contact between molten metal and the coolant.
[0008] Furthermore, many starter blocks permanently engage the emerging end of the ingot,
so that the end of the ingot and the block must be cut from the ingot. This leads
to undesirable waste of metal and the starter block.
[0009] It is therefore desirable to find shutdown methods and devices that will provide
quick isolation of particular strands and rapid draining and collection of molten
metal from all parts of the molten metal strand. It is also desirable to develop suitable
starter bocks which can ensure proper alignment of the emerging ingot, and reduce
chances of fire or explosion.
[0010] The disclosure makes it possible to use a remotely actuated shutoff device to terminate
flow through one or more connecting troughs. After termination of flow, the disclosure
also allows easy access to the connecting troughs and the mould.
[0011] US 4,178,000 discloses sealing a space between the walls of a cooled continuous casting mould
and the head of a starter bar by means of an elastic member in an annular peripheral
recess of the starter bar head. The preamble of claim 1 is based on this document.
[0012] FR 2779673 discloses a starter block having an anchoring means to which solidified metal becomes
attached. One form of the anchoring means is a threaded hole in a head of the starter
block into which molten metal is received.
DISCLOSURE OF THE INVENTION
[0013] The present disclosure thus provides, but not recited in the claims, an apparatus
for continuous casting of metal ingots, comprising a feed trough for carrying molten
metal, at least one casting mould for casting metal ingots and a connecting trough
separately connecting each casting mould to the feed trough for transferring molten
metal A shutoff gate is associated with each connecting trough and located adjacent
the feed trough, this gate being movable between an open position and a closed position.
Each connecting trough also includes a drop-down portion located between the shutoff
gate and the casing mould, this drop-down portion being adapted to swing downwardly
and thereby rapidly drain molten metal from the connecting trough and an entrance
of the mould.
[0014] The present invention provides, as defined by claim 1, an apparatus for continuous
casting of metal ingots, comprising a feed trough for carrying molten metal, a casting
mould for receiving molten metal, and casting the metal into metal ingots. A source
of coolant is positioned to impinge upon a surface of an ingot emerging from the mould
to cool the ingot and a conveying device is aligned in the direction of casting of
the ingot, for conveying the cast ingot from the casting mould. The apparatus also
includes an elongated starter block, adapted to be inserted into the mould and supported
by the conveying device and having a threaded recess formed therein for receiving
molten metal and an O-ring fitted to the starter block for sealing the block against
the casting mould. Further features of the apparatus of the present invention are
defined in claim 1.
[0015] The present disclosure provides, but not recited in the claims, a method of stopping
casting of at least one strand in a multi-strand continuous molten metal caster for
casting ingots. The caster has a feed trough for carrying molten metal, at least one
casting mould for casting metal ingots, a connecting trough separately connecting
each casting mould to the feed trough for transferring molten metal, a shutoff gate
associated with each connecting trough and located adjacent the feed trough, the gate
being movable between an open position and a closed position and each connecting trough
including a drop-down potion located between the shutoff gate and the casing mould,
the drop-down portion being adapted to swing downwardly. The method comprises closing
a shutoff gate to isolate at least one connecting trough from the feed trough and
swinging the drop-down portion downwardly to rapidly drain molten metal from the connecting
trough and an entrance of the mould.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The present invention will be described in conjunction with the following figures:
Fig. 1 is a perspective view of a two strand continuous horizontal caster for which
the present invention may be used, and downstream ingot-cutting equipment;
Fig. 2 is a perspective view of the two-strand horizontal caster, showing a shutoff
gate and drop-down portion, in its upright, operational position;
Fig. 3 is a perspective view of the two-strand horizontal caster, showing a shutoff
gate and drop-down portion in its downward, draining position;
Fig. 4a is a cross-sectional view of the horizontal continuous caster, showing the
drop-down portion in its upright, operational position;
Fig. 4b is a cross-sectional view of the horizontal continuous caster, showing the
drop-down portion in its downward, draining position;
Fig. 5 is a cross-sectional view of the casting mould showing the emerging ingot during
casting;
Fig. 6 is a flowchart of the steps for shutting down the horizontal continuous caster;
Fig. 7 is a cross-sectional view of the casting mould, holding the starter block of
the present invention; and
Fig. 8 is an elevation view of the starter block of the present invention.
BEST MODES FOR CARRYING OUT THE INVENTION
[0017] Fig. 1 shows a multi-strand horizontal casting machine 10, and in particular a two-strand
caster, with its associated downstream equipment. A three-strand casting machine is
shown in more detail in Fig. 2. Molten metal 12 travels from a common feed trough
14 to casting moulds 16 which form and produce cast ingots 18 of the desired cross
section shape and size. The casting moulds 16 are generally made of metal (e. g. aluminum)
body with a refractory entry tube, and may include graphite liners. Each mould 16
most commonly comprises a cooling jacket within the mould body connected to a first
coolant source for cooling the molten metal passing through it to form a skin on the
ingot.
[0018] Cast ingots are then carried away by conveying devices 52 for downstream processing.
[0019] Dedicated connecting troughs 20 connect each casting mould 16 to feed trough 14 to
form each strand of the multi-strand casting machine 10. A shutoff gate 22 is positioned
in each connecting trough 20 adjacent the feed trough 14. The shutoff gate 22 is open
for normal operation and can be closed to isolate individual strands from the molten
metal 12, in the case of a shut down. Each connecting. trough is provided with a drop-down
portion 24 adjacent the casting mould 16. This drop-down portion 24 remains in an
upright position for normal operation of the caster 10.
[0020] As seen in Fig. 3, the drop-down portion 24 can be lowered to a downwards position
during shutdown to rapidly drain molten metal from the isolated connecting trough
20 and the casting mould 16. Fig. 3 also illustrates one shutoff gate 22 in its closed
position to isolate the particular strand from the feed trough 14. Figs. 4a and 4b
are cross-sectional views showing respectively the operational and shutdown positions
of the drop-down portion 24. Each drop-down portion 24 is preferably in the form of
a block of refractory material with a passageway 25 therein to carry the molten metal.
This passageway 25 has an inlet in the top face of the block and an outlet in an end
face thereof, which align respectively with an outlet opening in the connecting trough
20 and an inlet opening to a mould 16. To assure a proper seal between the block 24
and the trough 14 and the mould 16, a Fiberfrax
™ paper is applied to the contacting faces.
[0021] The feed trough 14 and the connecting troughs 20 are preferably heated troughs. This
helps to keep the metal in molten form as it travels to the casting mould.
[0022] Although a feed trough 14 has been illustrated in Figs. 2 and 3 as being connected
to the casting moulds 16 via dedicated connecting troughs 20, it is to be understood
that the feed trough 14 can also be connected via a single header box (not shown)
for supplying molten metal to each casting mould 16. In this case, the shutoff gate
22 lies adjacent the header box to isolate it from the feed trough during shutdown.
[0023] As seen in Fig. 5, each casting mould 16 preferably includes a two piece mould body
17 machined from aluminum which includes an annular channel 26 within the mould body.
A refractory entry channel 19 can also be included with the mould 16, and that mates
at its inlet end with a downstream end of the drop-down trough section 24. The mould
is further lined with a graphite member 21. The channel 26 is connected to a second
coolant supply line 28 and includes at least one annular slot or a plurality of holes
32 running from the channel 26 to a surface of the casting mould 16 adjacent the emerging
ingot 18. Coolant from the second coolant supply line 28 flows out through the slot
or holes 32 to impinge against the skin formed on the emerging ingot 18, thereby cooling
and solidifying the ingot 18. A gas supply line 30 is also connected to the channel
26 to supply gas for clearing the slot or holes 32 of coolant and preventing the entry
of molten metal 12. Another embodiment of mould suitable for use is described in
US Patent No. 7,079,186.
[0024] The flowchart of Fig. 6 illustrates some possible reasons for shutting down a particular
strand of a multi-strand casting machine 10, and the subsequent steps that can be
taken to isolate and shut down the strand. The breakout detector may be any sensor
capable of identifying a liquid metal leak from the mould, but is preferably one as
described in
US Patent 6,446, 704 (Collins). Other faults that may cause the sequence of events in the flowchart to occur include
failure of a cutoff saw used to cut the continuously emerging ingot into sections
or loss of synchronization between the ingot withdrawal mechanism and the ingot movement.
The apparatus that may give rise to these types of shutdown events is described in
US Patent No. 7,028,750.
[0025] In a first step, the particular strand is isolated from the feed trough 14 or from
the reservoir, depending on the configuration, by closing the shutoff gate 22. The
shutoff gate 22 is preferably biased closed and includes an actuator for holding the
gate in an open position for normal operation. Suitable shutoff gates can include,
for example normally closed gate valves. The next step is to lower the drop-down portion
24 to a downwards position so as to rapidly drain any molten metal 12 from the connecting
trough 20 and the casting mould 16. The molten metal 12 can then be collected via
channels 33 into dump bins 34, such as those illustrated in Fig. 1.
[0026] Between closing the shutoff gate 22 and lowering the drop-down portion 24, it is
preferable to accelerate the rate of withdrawal of the ingot 18 by the conveying device
52 to clear the exit of the casting mould 16 and isolate the strand. After the drop-down
portion is lowered, a further preferred step is to stop coolant flow from the coolant
supply line 28 to the ingot 18. A final preferred step is to inject gas from the gas
supply line 30 to the annular channel 26 and through the outlet holes 32 to clear
these holes 32 of coolant and molten metal.
[0027] Figs. 7 and 8 show a starter block 36 for starting up or restarting a particular
strand. The block 36 is generally elongated and sized at one end to be inserted in
the mouth of the mould 16 and supported on the conveying device 52. A threaded, conical,
recess 38 is formed in the block 36, parallel to the direction of flow of molten metal,
for receiving molten metal. The starter block further comprises a circumferential
groove 48 for receiving an O-ring 40. The O-ring 40 is adapted to engage the mouth
of the casting mould 16 to positively seal the block 36 against the casting mould
16.
[0028] The starter block 36 has a concave annular depression 42 adjacent the mould 16 adapted
to deflect coolant away from the O-ring 40 thereby preventing contact between the
coolant and the molten metal. The starter block 36 further or alternatively comprises
an air vent 44, formed between the threaded recess 38 and a surface of the starter
block 36, to allow venting of air from the recess 38 as it receives molten metal 12.
Preferably, a porous plug 46 is provided in the recess 38 at the entrance to the air
vent 44 that allows venting of air from the recess 38 while preventing molten metal
from passing through the vent 44.
[0029] As the molten metal 12 passes through the casting mould 16 and cools to form a skin
on the ingot 18, the starter block 36 disengages from the mouth of the mould 16 and
exposes the ingot to the impinging coolant streams, thereby cooling and further solidifying
the ingot 18. The starter block can then be unthreaded from the ingot for re-use.
FEATURES OF THE PRESENT DISCLOSURE
[0030]
- 1. An apparatus for continuous casting of metal ingots, comprising:
- (a) a feed trough for carrying molten metal;
- (b) at least one casting mould for casting metal ingots;
- (c) a connecting trough separately connecting each said casting mould to the feed
trough for transferring molten metal;
- (d) a shutoff gate associated with each connecting trough and located adjacent the
feed trough, said gate being movable between an open position and a closed position;
and
- (e) each connecting trough including a drop-down portion located between the shutoff
gate and the casting mould, said drop-down portion being adapted to swing downwardly
and thereby rapidly drain molten metal from the connecting trough and an entrance
of the mould.
- 2. The apparatus of 1 wherein the drop-down portion of the connecting trough is pivotably
mounted on one end thereof.
- 3. The apparatus of 2 wherein the shut-off gate is biased closed and further comprises
an actuator for holding the gate in an open position.
- 4. The apparatus of 1 further comprising:
- (a) an annular channel formed in the casting mould having a coolant inlet to the channel
and at least one opening for delivering coolant from the annular channel to a surface
of the ingot during casting; and
- (b) a gas supply line connected to the annular channel for periodic injection of gas
to clear the at least one opening of coolant or molten metal.
- 5. The apparatus of 1 wherein the feed trough is a heated trough.
- 6. The apparatus of 1 wherein the at least one connecting trough is a heated trough.
- 7. The apparatus of 1 further comprising a conveying device, positioned adjacent the
mould and aligned in the direction of casting of the ingot, for conveying the ingot
from the casting mould.
- 8. An apparatus for continuous casting of metal ingots, comprising:
- (a) a feed trough for conveying molten metal;
- (b) at least one casting mould for casting metal ingots;
- (c) a connecting trough separately connecting each said casting mould to the feed
trough for transferring molten metal;
- (d) a shutoff gate associated with each connecting trough and located adjacent the
reservoir, said gate being movable between an open position and a closed position;
- (e) each connecting trough including a drop-down portion located between the shutoff
gate and the casing mould, said drop-down portion being adapted to swing downwardly
and thereby rapidly drain molten metal from the connecting trough and an entrance
of the mould;
- (f) a conveying device associated with each casting mould aligned in the direction
of casting of the ingot, for conveying the cast ingot from the casting mould;
- (g) a elongated starter block, adapted to be inserted into the mould and supported
by the conveying device and having a threaded recess formed therein for receiving
molten metal; and
- (h) an O-ring fitted to the starter block for sealing the block against the casting
mould.
- 9. A method of stopping casting of at least one strand in a multi-strand continuous
molten metal caster for casting ingots, having a feed trough for carrying molten metal,
at least one casting mould for casting metal ingots, a connecting trough separately
connecting each said casting mould to the feed trough for transferring molten metal,
a shutoff gate associated with each connecting trough and located adjacent the reservoir,
said gate being movable between an open position and a closed position, each connecting
trough, including a drop-down portion located between the shutoff gate and the casing
mould, said drop-down portion being adapted to swing downwardly, the method comprising:
- a. closing the shutoff gate to isolate said at least one strand from the feed trough;
and
- b. swinging the drop down portion downwardly to rapidly drain molten metal from the
connecting trough and an entrance of the mould.
- 10. The method of 9 further comprising, between closing the shutoff gate and swinging
the drop down portion downwardly, accelerating the rate of extracting of the ingot
from the mould.
- 11. The method of 9 wherein the casting mould is provided with an annular channel
having a coolant inlet and at least one opening for delivering coolant to a surface
of the ingot during casting, and an air supply line and air supply valve connected
to the annular channel for clearing the at least one opening of coolant or molten
metal,
the method comprising shutting off the coolant inlet and injecting a gas from the
air supply line through the at least one opening, to clear the opening, after swinging
the drop-down portion downwardly.
1. An apparatus (10) for continuous casting of metal ingots (18), comprising:
(a) a trough (14, 20) for carrying molten metal;
(b) a casting mould (16) for receiving molten metal, and casting the metal into metal
ingots;
(c) a source of coolant positioned to impinge upon a surface of the ingot to cool
said ingot;
(d) a conveying device (52), aligned in the direction of casting of the ingot, for
conveying the cast ingot from the casting mould;
(e) an elongated starter block (36), adapted to be inserted into the mould and supported
by the conveying device; and
(f) an O-ring (40) fitted to the starter block for sealing the block against the casting
mould; characterised by:
the elongated starter block having a threaded recess (38) formed therein for receiving
molten metal;
wherein the starter block further comprises an air vent (44), formed in the threaded
recess and leading to an adjacent surface of the starter block, to allow venting of
air from the recess as it receives molten metal; and/or
wherein the starter block has a concave annular depression (42) on an outer face thereof
adjacent the mould adapted to deflect coolant away from the 0-ring.
2. The apparatus of claim 1 further comprising a porous plug (46) placed in the threaded
recess adjacent the air vent to hold molten metal in the recess while allowing venting
of air from the recess.
1. Vorrichtung (10) zum kontinuierlichen Gießen von Metall-Gussblöcken (18), mit:
(a) einer Rinne (14, 20) zum Führen geschmolzenen Metalls;
(b) einer Gussform (16) zum Aufnehmen geschmolzenen Metalls und zum Gießen des Metalls
in Metall-Gussblöcke;
(c) einer Kühlmittelquelle, die angeordnet ist, um die Oberfläche des Gussblocks zu
beaufschlagen und den Gussblock zu kühlen;
(d) einer Fördereinrichtung (52) zum Abtransportieren des gegossenen Gussblocks aus
der Gussform, ausgerichtet in Gussrichtung des Gussblocks;
(e) einem gestreckten Starterblock (36), der ausgeführt ist, um in die Form eingebracht
zu sein und durch die Fördereinrichtung gehalten ist; und
(f) einem O-Ring (40), der an dem Starterblock befestigt ist, um den Blocks gegen
die Gussform abzudichten;
gekennzeichnet dadurch, dass:
der gestreckte Starterblock eine darin vorgesehene, mit einem Gewinde versehene Ausnehmung
(38) zum Aufnehmen geschmolzenen Metalls, aufweist;
wobei der Starterblock ferner eine Entlüftung (44) aufweist, die in der mit dem Gewinde
versehenen Ausnehmung ausgebildet ist und zu einer an den Starterblock angrenzende
Fläche führt, um die Entlüftung von Luft aus der Ausnehmung, wenn diese geschmolzenes
Metall aufnimmt, zu gestatten; und/oder
wobei der Starterblock an einer äußeren Fläche desselben eine konkave kreisringförmige
Vertiefung, angrenzend an die Form aufweist, die ausgeführt ist, um Kühlmittel weg
von dem O-Ring zu lenken.
2. Vorrichtung gemäß Anspruch 1, weiter mit einem porösen Verschluss (46), der in der
mit dem Gewinde versehenen Ausnehmung, angrenzend an die Entlüftung platziert ist,
um geschmolzenes Metall in der Ausnehmung zu halten, während die Entlüftung von Luft
aus der Ausnehmung gestattet ist.
1. Appareil (10) destiné à couler en continu des lingots de métal (18), comprenant :
(a) une goulotte (14, 20) pour acheminer le métal fondu ;
(b) une lingotière (16) pour recevoir le métal fondu, et mouler le métal en lingots
de métal ;
(c) une source de fluide de refroidissement positionnée de façon à affecter une surface
du lingot pour refroidir ledit lingot ;
(d) un dispositif de transport (52) aligné dans la direction de la coulée du lingot,
pour transporter le lingot coulé à partir de la lingotière ;
(e) un bloc d'amorçage allongé (36) adapté pour être inséré dans le moule et supporté
par le dispositif de transport ; et
(f) un joint torique (40) ajusté sur le bloc d'amorçage pour sceller le bloc contre
la lingotière ;
caractérisé en ce que :
le bloc d'amorçage allongé présente un renfoncement fileté (38) formé à l'intérieur
pour recevoir le métal fondu ;
dans lequel le bloc d'amorçage comprend en outre un évent (44) formé dans le renfoncement
fileté et conduisant à une surface adjacente du bloc d'amorçage, afin de permettre
l'évacuation de l'air à partir du renfoncement quand il reçoit le métal fondu ; et/ou
dans lequel le bloc d'amorçage présente une dépression annulaire concave (42) sur
une face extérieure de celui-ci adjacente au moule, adaptée pour dévier le fluide
de refroidissement à partir du joint torique.
2. Appareil selon la revendication 1, comprenant en outre un bouchon poreux (46) placé
dans le renfoncement fileté adjacent à l'évent afin de contenir le métal fondu dans
le renfoncement tout en permettant l'évacuation de l'air à partir du renfoncement.